not enough free storage space to install selected instruments and loops

It's a typical issue when you have less storage space on your system drive than is required to download the installation packages for LPX content. This happens because, if you try to download and install the rest of the sound library in one go, Logic will first download all the installation packages to the system drive, and only then install them to external. Needless to say that this process would require twice the storage space.

The remedy is to download libraries using Sound Library Manager (Logic Pro X > Sound Library > Open Sound Library Manager) one by one. A bit tedious, but there's no other workaround. In Sound Library Manager you can tick particular libraries for installation and it will display their size. Make sure to download content in chunks no more than 10-15 Gb.

hx103: The entire Logic library takes about 80 Gb of disk space. As I pointed out above, if you try to download everything at once, you'll need twice the space on the system drive. You may still be able to install all libraries if you download them one by one.

I just bought a new Macbook Pro 128 GB and when I go to the sound library manager, it's grayed out...? And I'm receiving the same error anyhow. How much space does Logic need? I guess I'll just need an external hard drive.